I got my GMB dirty for the first time yesterday. Tried 44 cal XTP300 gr / hornady green sabot over 110 goex 2f not happy. Too much charge i think. Also tried great plains 385 gr over 90 gr 2f much better. best results of the day were with... you guessed it 320 gr REAL over 90 gr 2f. 5 shot group under a loonie (Canadian dollar coin) Maybe I was just getting used to the fiber optic sights. I don't really like them asI get a double image of each light dot even with one eye closed. More homework is probably needed but I get the feeling the REAL 320s are my best load for now.